The most common cause of a malfunctioning Skross adapter is a blown fuse and you can replace the fuse in your World Adapter Pro with the Skross 6.3A miniature fuse: Take a screwdriver or a coin, place it in the slot at the bottom and turn it lightly to the left. Insert a new fuse of the appropriate strength into the holder and fix it back into the adapter.
If the fuses in your Skross adapter blow due to overloading, we have the right spare parts for you here.